High brightness LEDs are being introduced in an increasingly number of illumination applications. The steady progress made in LED development with respect to efficiency, brightness and color control enables the penetration of new lighting markets, such as automotive front lighting or general illumination.
Conventional high brightness LEDs emit from the top of the die surface, typically in a 1×1 mm area. As the LEDs emit a rather narrowband wavelength range, they exist in various colors, such as blue, green, amber, red. For instance, for white light emission production, phosphor compositions can be applied that convert part of blue LED emission to higher wavelengths, enabling the emission of white light in various color temperatures. High brightness LEDs are also an attractive choice for backlight applications, such as backlights in display devices and the like.
For backlighting purposes, side-emitting devices are preferred. For many applications, such as hand held devices, mobile phones, PDAs and the like, a thin, small sized backlight arrangement is also desired. One side emitting configuration suitable for use together with top-emissive LEDs is described in GB 2 428 859 A, Avago Technologies. Here is described a back light arrangement for a display device. A curved reflector overlies the LED to redirect the emitted light in a direction essentially parallel to the substrate on which the LED is arranged. The redirected light is introduced in a light pipe comprising features at the bottom surface that redirect light in the light pipe towards the front surface thereof, out from the light pipe and into a light conversion layer. Problems with the arrangement in GB 2 428 859 includes however that it requires a significant thickness and surface area in order to emit the light sidewise. The curved reflector has a much larger footprint than the LED it self. Further, the color conversion into the desired color requires an additional large area light conversion layer separate from the actual side emitter. Hence, there is a need in the art for more compact side emitting devices.